The invention relates generally to a torque limiting sprocket assembly and more particularly to a chain sprocket assembly having an integral torque limiting clutch. The assembly may be advantageously, though not exclusively, used in motor vehicle transfer cases and other vehicle power train components.
The delivery of power and specifically drive torque in a four-wheel drive motor vehicle from a primary drive line which is continuously active to a secondary drive line which may deliver torque to a secondary set of drive wheels on a part time basis is the subject of much study and innumerable mechanical configurations and operating routines. Generally speaking, a clutch operably resides between the primary and secondary drive lines in a transfer case and delivers torque from the primary drive line to the secondary drive line. The clutch may take many forms: a straightforward mechanical device such as a dog clutch having only fully engaged and fully released operating states, an overrunning clutch which engages only when a speed difference exists between the drive lines, a viscous clutch which is always operational and provides increasing resistance with increasing speed difference between the primary and secondary drive lines and an electrically or hydraulically modulatable friction clutch which may be controlled according to diverse programs and operating sequences to apportion torque delivery to the primary and secondary drive lines from 100% to the primary drive line (0% to the secondary drive line) to a 50%xe2x80x9450% torque split between the drive lines and typically at many or an infinite number of levels therebetween.
Particularly in the two stage (on-off) systems but in the overrunning, viscous and modulatable systems as well, it may be beneficial to limit the maximum torque delivered to the secondary drive line wheels. For example, a particular vehicle weight, weight distribution or intended service environment may dictate limiting the torque delivered to the secondary (typically front) axle and wheels of a four wheel drive vehicle in order to provide optimum performance. Similarly, it may be desirable from an overall vehicle operation standpoint to limit the maximum torque delivered to the secondary axle and wheels.
The present invention relates to a torque limiting assembly which may be disposed integrally with one the chain sprockets in the chain drive assembly of a typical transfer case.
A chain sprocket assembly for use in a motor vehicle transfer case includes a torque limiting clutch which limits the torque provided to a secondary drive line. The chain sprocket assembly includes a chain receiving collar having an inwardly extending annular member which is received between two friction clutch packs. The friction clutch packs are operably disposed between the chain receiving collar and a circular housing which is splined to a secondary output shaft of the transfer case. A spring biasing mechanism which engages outer faces of the clutch packs and compresses them against the annular member of the chain receiving collar may be adjusted to provide a desired compressive force to achieve a desired maximum torque throughput from the chain to the secondary output shaft. In operation, the chain sprocket assembly will transmit torque to the secondary output shaft and the secondary drive line up to the preset maximum and which threshold the friction clutch packs will slip, thus limiting torque throughput to the preselected level.
Thus, it is an object of the present invention to provide a chain sprocket having an integral torque limiting clutch.
It is a further object of the present invention to provide a chain sprocket having an integral torque limiting clutch which may be disposed in a transfer case or other motor vehicle power train component.
It is a still further object of the present invention to provide a torque limiting clutch assembly which may be disposed within a chain sprocket in the chain drive assembly of a motor vehicle transfer case or similar vehicle power train component.
Further objects and advantages of the present invention will become apparent by reference to the following description of the preferred and alternate embodiments and appended drawings wherein like reference numbers refer to the same component, element or feature.